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<p>Wumuite, ideally <span class="inline-formula">KAl_0.33W_2.67O₉</span>, is a new mineral species found in the Neoproterozoic Sinian light-weathered biotite–quartz monzonite in the southern part of the Panzhihua–Xichang region (Nanyang village: 26<span class="inline-formula">^∘</span>46<span class="inline-formula">^′</span>8.21<span class="inline-formula">^′′</span>&thinsp;N, 101<span class="inline-formula">^∘</span>27<span class="inline-formula">^′</span>13.86<span class="inline-formula">^′′</span>&thinsp;E), China. It is associated with quartz, orthoclase, albite, biotite, hornblende, kaolinite, ilmenite, goethite, hematite, zircon, zoisite, tourmaline, monazite-(Ce), allanite-(Ce), scheelite, tellurite, tewite, and an unidentified, potentially new mineral corresponding to <span class="inline-formula">WO₃</span>. Wumuite occurs as light green hexagonal tabular crystals, is up to 0.3&thinsp;mm in diameter, and has a vitreous to adamantine luster and a white streak; i.e., it is transparent. The mineral is brittle with good cleavage parallel to <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M10" display="inline" overflow="scroll" dspmath="mathml"><mrow><mo mathvariant="italic">{</mo><mn mathvariant="normal">10</mn><mover accent="true"><mn mathvariant="normal">1</mn><mo mathvariant="normal">¯</mo></mover><mn mathvariant="normal">0</mn><mo mathvariant="italic">}</mo></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="38pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="8df949e7ba275a3ebabc9825b76cabbb"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-32-483-2020-ie00001.svg" width="38pt" height="14pt" src="ejm-32-483-2020-ie00001.png"/></svg:svg></span></span> and <span class="inline-formula"><i>{</i>0001<i>}</i></span>. It has a Mohs hardness of about 5–6 and a calculated density of 6.52&thinsp;<span class="inline-formula">g cm⁻³</span>. Electron microprobe analyses yielded the following (in wt&thinsp;% – average of 10 spot analyses of one sample): <span class="inline-formula">K₂O</span> 5.55, <span class="inline-formula">WO₃</span> 91.16, <span class="inline-formula">TeO₂</span> 0.59, and <span class="inline-formula">Al₂O₃</span> 2.52, with a total of 99.82. The empirical formula for wumuite calculated on the basis of <span class="inline-formula">O_apfu=9</span> is <span class="inline-formula">K_0.80(W_2.68Al_0.34Te_0.03)_∑3.05O₉</span>, ideally <span class="inline-formula">K(W_2.67Al_0.33)_∑3O₉</span> or <span class="inline-formula">KAl_0.33W_2.67O₉</span>. The strongest four diffraction lines [<span class="inline-formula"><i>d</i></span>&thinsp;Å (<span class="inline-formula"><i>I</i></span>) (<i>hkl</i>)] are 6.261(36)(010), 3.727(30)(001), 3.161(100)(020), and 2.413(40)(021). Wumuite is hexagonal, in space group <span class="inline-formula"><i>P</i></span>6<i>/mmm</i>, with <span class="inline-formula"><i>a</i>=7.2952(5)</span>&thinsp;Å, <span class="inline-formula"><i>c</i>=3.7711(3)</span>&thinsp;Å, <span class="inline-formula"><i>V</i>=173.81(2)</span>&thinsp;Å<span class="inline-formula">³</span>, and <span class="inline-formula"><i>Z</i>=1</span>. The crystal structure was solved and refined to a reliability factor of <span class="inline-formula"><i>R</i>₁</span>[<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M30" display="inline" overflow="scroll" dspmath="mathml"><mrow><msup><mi>F</mi><mn mathvariant="normal">2</mn></msup><mo>&gt;</mo><mn mathvariant="normal">4</mn><mi mathvariant="italic">σ</mi><mo>(</mo><msup><mi>F</mi><mn mathvariant="normal">2</mn></msup><mo>)</mo><mo>]</mo><mo>=</mo><mn mathvariant="normal">0.025</mn></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="104pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="d5b4922c97500b973285c5cf232c1ced"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="ejm-32-483-2020-ie00002.svg" width="104pt" height="15pt" src="ejm-32-483-2020-ie00002.png"/></svg:svg></span></span> (<i>wR</i><span class="inline-formula">₂=0.072</span>) based on 164 unique reflections (777 measured reflections, <span class="inline-formula"><i>R</i>_(int)=0.011</span>). Wumuite has a hexagonal tungsten bronze (HTB)-type structure. The layers of corner-sharing <span class="inline-formula">[(W,Al)O]₆</span> octahedra, with the layers oriented normal to the short (3.7713&thinsp;Å) <span class="inline-formula"><i>c</i></span> repeat and along with the W–O–W links, connect to form a hexagonal ring channel (tunnel). K is distributed in the hexagonal channel. An associated new mineral, tewite, which was discovered in the same area, also has a new tungsten bronze (TB)-type-related structure and has a genetic connection with wumuite in both back-scattered electron (BSE) images and synthetic experiments. The formation of wumuite is likely related to the nearby quartz-vein-type Au mineralization. The mineral was formed by a metasomatic reaction between W-rich hydrothermal fluids and the potassium feldspar in the monzonite.</p>